code: def test_mark_groups(self):
      plt.close("all")
      g = Graph.Ring(5, directed=True)
      fig, ax = plt.subplots()
      plot(
          g, target=ax, mark_groups=True, layout=self.layout_small_ring
      )
  
imports: import os
  import unittest
  from igraph import Graph, plot, VertexClustering, Layout
  from ...utils import overridden_configuration
label_desc: Use image node_id 8 for calling the GraphTestRunner obj's underlying member method code with example usage: obj.test_mark_groups() without return types